Rats administered monoamine neurotoxins recover differently in isolated and enriched environments. They show progressive behavioral improvement in enriched, social environments but behavioral oscillations in isolated environments. These stages of recovery are correlated with alterations in biochemical measures of the monoamine neurotransmitter systems predominantly damaged by the neurotoxins. Other rats implanted with slow-release amphetamine pellets made from silicone show a characteristic progression in behavioral alterations. They are initially hyperactive and exploratory, then enter intense stereotypies from 1-3 days after implantation. They then retire to the burrows on day 4, and thereafter are characterized by increased startle responses and heightened social behaviors involving fight and flight. This late phase of constant amphetamine intoxication is similar to amphetamine psychosis in humans, and it is correlated with alterations in dopamine innervations to the caudate nucleus.